title: Red-light-controllable liquid-crystal soft actuators via low-power excited upconversion based on triplet-triplet annihilation.
abstract: A red-light-controllable soft actuator has been achieved, driven by low-power excited triplet-triplet annihilation-based upconversion luminescence (TTA-UCL). First, a red-to-blue TTA-based upconversion system with a high absolute quantum yield of 9.3 ± 0.5% was prepared by utilizing platinum(II) tetraphenyltetrabenzoporphyrin (PtTPBP) as the sensitizer and 9,10-bis(diphenylphosphoryl)anthracene (BDPPA) as the annihilator. In order to be employed as a highly effective phototrigger of photodeformable cross-linked liquid-crystal polymers (CLCPs), the PtTPBP&BDPPA system was incorporated into a rubbery polyurethane film and then assembled with an azotolane-containing CLCP film. The generating assembly film bent toward the light source when irradiated with a 635 nm laser at low power density of 200 mW cm(-2) because the TTA-UCL was effectively utilized by the azotolane moieties in the CLCP film, inducing their trans-cis photoisomerization and an alignment change of the mesogens via an emission-reabsorption process. It is the first example of a soft actuator in which the TTA-UCL is trapped and utilized to create photomechanical effect. Such advantages of using this novel red-light-controllable soft actuator in potential biological applications have also been demonstrated as negligible thermal effect and its excellent penetration ability into tissues. This work not only provides a novel photomanipulated soft actuation material system based on the TTA-UCL technology but also introduces a new technological application of the TTA-based upconversion system in photonic devices.
authors.affiliation: Department of Materials Science & State Key Laboratory of Molecular Engineering of Polymers, Fudan University , Shanghai 200433, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Jiang
authors.forename: Ming
authors.initials: M
authors.lastname: Xu
authors.forename: Fuyou
authors.initials: F
authors.lastname: Li
authors.forename: Yanlei
authors.initials: Y
authors.lastname: Yu
mesh_terms: D000873:Anthracenes / Q000737:chemistry*; D007834:Lasers; D050866:Liquid Crystals / Q000737:chemistry*; D049449:Luminescence; D055617:Micro-Electrical-Mechanical Systems; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry; D009943:Organophosphorus Compounds / Q000737:chemistry*
chemical_list: D000873:Anthracenes; D009942:Organometallic Compounds; D009943:Organophosphorus Compounds